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Need help with rotation question

  1. Jan 27, 2006 #1
    Please refer to the drawing located at http://www.pineridge7.com/sw3/images/plan.jpg for reference.

    My plan is to make a simple rotational device. As the slide is manually pushed the length of the stationary bed the rack assembly will follow the angled 1" rod (slide). The rack assembly will move toward the bed rotating the pinion gear and jack-shaft. I am needing the jack-shaft to make but one complete revolution per every 4 foot of bed travel. The angle of the 1" rod (slide) can be changed and locked into position by the adjustmant rod and T-locks.

    Is the size and pitch of the rack assembly/pinion gear critical for this rotation per length or will the adjustment rod make the machine flexible enough to use most and rack and pinion that I come across?
  2. jcsd
  3. Jan 27, 2006 #2


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    The angled rod complicates things since now you need to use trig, and if the rack should not be perpendicular to the slide the rotation would be off, along with the backlash of the rack/pinnion.

    Instead, a 15.28" diameter wheel with a string attached to one end would offer a single rotation per 4' of linear travel, and the cicumfrence could be marked to offer per inch increments easily enough. If you need rotation inline with the slide motion, you could use two bevel gears to transfer the rotation to that axis.
  4. Jan 27, 2006 #3
    Cliff I am attempting to duplicate a machine that has been used successfully in Sweden for some years to bore rifle barrels. A picture of the working model may be seen at this link.
  5. Jan 27, 2006 #4


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    Well, since you are not using it to measure something where positional accuracy is important, then yes it would be pretty simple to adjust the offset to dial in the single revolution.

    I'd consider trying to use a medium to larger pinion, it will require a longer offset for the angled bar but would give you a little more leverage on the turning of that shaft. By larger I mean something like a 48 tooth on a 24 pitch rack.
  6. Jan 28, 2006 #5
    Cliff thanks very much for your suggestion, we will follow your advice. This is just the kind of information that I was seeking.

    I'm off to MacMaster.com to see what they have to offer in rack & pinions. Anyone know of an alternative source for these items?
  7. Jan 28, 2006 #6


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    You'll have better luck with mcmaster.com :smile:

    I've had good experience with McMaster-Carr and with a nearby location the shipping is very prompt. Another choice might be sdp-si.com but haven't ordered from them yet, and there are a few other sources as well. You can even find a slightly (or heavily) used gears on ebay once in a while, stuff that would otherwise be quite a bit more expensive. You can even get new-in-box precision THK linear bearings quite reasonable sometimes. Worth a search (or 100), a deal happens once in a while on there with some leftover item.
  8. Jan 28, 2006 #7


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    McMaster is always the best. No doubt about it. If you need another source, you can also try Grainger.

    Looking at this, is the travel requirement on the slide a requirement for proper rifling? I occasionally use a shope here to help manufacture prototype shafts. They specialize in gun boring. It's interesting stuff.
  9. Jan 28, 2006 #8

    Fred by increasing or decreasing the angle of the shaft on the right you can increase or decrease the number of revolutions per any given travel. However the length of the slide travel is not critical. most machines that I am aware of are shorter than the one I am building to handle pistol barrels.
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